feat/stream large files

[forgetso]

• Stream large files
• docs(changeset): Stream large files to avoid loading entire file into RAM

[Copilot]

Pull request overview

This PR updates the @prosopo/util caching utilities to stream remote file downloads to disk (instead of buffering the entire response in memory), improving memory usage when working with large files.

Changes:

• Change fetchWithETag to return a ReadableStream (plus optional contentLength) instead of a full string payload.
• Update cacheFile / saveFileWithETag to write fetched content to disk via streaming.
• Update unit tests and add a changeset entry documenting the streaming change.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 7 comments.

File	Description
packages/util/src/tests/cacheFile.unit.test.ts	Updates tests to mock streamed content instead of string content.
packages/util/src/fetchWithEtag.ts	Returns a response body stream (and parses content-length) instead of response.text().
packages/util/src/cacheFile.ts	Streams writes to the cache file and makes saveFileWithETag async.
.changeset/better-maps-sin.md	Adds a changeset entry for the util package release.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

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